Magnetically actuated roller head

ABSTRACT

A magnetically actuated roller head includes a linear actuator mountable on an end of a multi-axis robotic arm. The linear actuator includes a slide, a magnet operably connected to the slide and operable to urge the slide in a linear direction, and a connector disposed on a distal end of the slide. A roller hemming head is mounted on the linear actuator by the connector. The roller hemming head includes at least one hem roller.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the priority of U.S. Provisional Application No.61/070,551 filed Mar. 24, 2008.

TECHNICAL FIELD

This invention relates to robotic roller hemming, and more particularlya robotic roller head used for robotic roller hemming such as hemming ofvehicle closure panels.

BACKGROUND OF THE INVENTION

It is known in the art relating to actuation of a roller hemming headthat conventional actuators typically require one or more of thefollowing: hydraulics, pneumatics, electric cylinders, gas springcharge, monitoring of air or gas pressure, and oil disposal. Theserequirements may elevate the cost, size, and complexity of aconventional roller hemming head.

SUMMARY OF THE INVENTION

The present invention provides a magnetically actuated roller hemminghead that utilizes magnetic and/or electromagnetic force to actuate aroller hemming head and to provide a hemming force through a hem rollerof the roller hemming head. The present invention may allow for variableforce control on the roller head with instantaneous response time toroller head force changes. The present invention also may eliminate theneed for some or all of the following: hydraulics, pneumatics, electriccylinders, gas spring charge, monitoring of air or gas pressure, and oildisposal.

More particularly, a magnetically actuated roller head in accordancewith the present invention includes a linear actuator mountable on anend of a multi-axis robotic arm. The linear actuator includes a slide, amagnet operably connected to the slide and operable to urge the slide ina linear direction, and a connector disposed on a distal end of theslide. A roller hemming head is mounted on the linear actuator by theconnector. The roller hemming head includes at least one hem roller.

Optionally, the magnet may be a rare earth magnet. Alternatively, thelinear actuator may include a rare earth magnet disposed between twoopposing magnets. The polarity of one of the opposing magnets may bedisposed in the same direction as the polarity of the rare earth magnet,and the polarity of the other of the opposing magnets may be disposed inan opposite direction to the polarity of the rare earth magnet.Optionally, the two opposing magnets may be rare earth magnets.Alternatively, the linear actuator may include an electromagnet disposedon each of opposite sides of the magnet. The electromagnets control andassist a force transmitted by the magnet.

Also, the slide may include an anti-rotate feature.

In another embodiment, a magnetically actuated roller head includes ahousing having an internal bore. The housing is mountable on an end of amulti-axis robotic arm. A pair of opposing actuator members are fixedlymounted within the inner bore. A shaft extends through the actuatormembers. A magnet is mounted on the shaft and is moveable within theinner bore. The magnet is disposed between the actuator members. A slideis connected to the shaft and extends outwardly from the housing. Aconnector is disposed on a distal end of the slide. A roller hemminghead is mounted on the connector. The roller hemming head includes atleast one hem roller. The actuator members control and assist a hemmingforce applied by the roller hemming head through the magnet.

Optionally, the magnet may be a rare earth magnet. Also, the actuatormembers may be rare earth magnets. The polarity of one of the actuatormembers may be disposed in the same direction as the polarity of therare earth magnet, and the polarity of the other of the actuator membersmay be disposed in an opposite direction to the polarity of the rareearth magnet. Alternatively, the actuator members may be electromagnets.

The housing may include an anti-rotate linear guide, and the slide mayinclude an anti-rotate feature cooperable with the linear guide. Theanti-rotate feature may be one of a spline, a ball spline, and a squarelinear bearing.

A method of roller hemming in accordance with the present inventionincludes mounting a linear actuator on an end of a multi-axis roboticarm, the linear actuator including a slide, a magnet operably connectedto the slide and operable to urge the slide in a linear direction, and aconnector disposed on a distal end of the slide; and mounting a rollerhemming head on the linear actuator by the connector, the roller hemminghead including at least one hem roller. The linear actuator provides ahemming force for performing roller hemming operations with the hemroller.

Optionally, the magnet may be a rare earth magnet. The method may alsoinclude disposing the magnet between a pair of opposing actuatormembers. The actuator members may be rare earth magnets. Alternatively,the actuator members may be electromagnets.

The method may also include restricting axial rotation of the rollerhemming head by providing a spline on the slide. Also, the method mayinclude providing a plurality of different hem rollers on the rollerhemming head.

These and other features and advantages of the invention will be morefully understood from the following detailed description of theinvention taken together with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a sectional view of a magnetically actuated roller head inaccordance with a first embodiment of the present invention;

FIG. 2 is a sectional view of a magnetically actuated roller head inaccordance with a second embodiment of the present invention for pushtype roller hemming;

FIG. 3 is a sectional view of a magnetically actuated roller headsimilar to the embodiment of FIG. 2 for pull type roller hemming;

FIG. 4 is a sectional view of a magnetically actuated roller head inaccordance with a third embodiment of the present invention for pushtype roller hemming; and

FIG. 5 is a sectional view of a magnetically actuated roller headsimilar to the embodiment of FIG. 4 for pull type roller hemming.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings in detail, numeral 110 generally indicatesa magnetically actuated roller head in accordance with the presentinvention. The magnetically actuated roller head utilizes magneticand/or electromagnetic force to actuate a roller hemming head and toprovide a hemming force through a hem roller of the roller hemming head.

With reference to FIG. 1, in a first embodiment the magneticallyactuated roller head 110 includes a linear actuator 112 mountable on anend of a multi-axis robotic arm (not shown). A roller hemming head 114is mounted on the linear actuator 112. The linear actuator 112 providesa hemming force for performing roller hemming operations with the rollerhemming head 114.

The linear actuator 112 includes a housing 116 that has an inner bore118 that generally extends through the housing. An end cap 120 ismounted on an end of the housing 116 and closes an end of the inner bore118. The end cap 120 may include a feature such as a mounting surfacefor mounting the linear actuator 112 on a robotic arm.

A pair of opposing actuator members 122 are fixedly mounted within theinner bore 118. A shaft 124 extends through the actuator members 122. Amagnet 126 is mounted on the shaft 124 and is moveable within the innerbore 118. The magnet 126 is disposed between the actuator members 122.More specifically, in the first embodiment the actuator members 122 maybe electromagnetic coils and the magnet 126 may be a polarized magnethaving its north and south poles disposed in an axial direction relativeto the shaft 124. Further, a pair of moveable yokes 128 made of a softmagnetic material sandwich the polarized magnet 126. The polarizedmagnet 126 and yokes 128 are fixedly mounted on the shaft 124 and aredisposed between and within the electromagnetic coils 122. The magneticfield of the polarized magnet 126 forms a magnetic circuit that passesthrough the polarized magnet 126, the moveable yokes 128, and theelectromagnetic coils 122.

An end 130 of the shaft 124 is supported by the end cap 120. Forexample, the end 130 may include a bushing engaged with a bushing hole132 in an inner surface of the end cap 120. An opposite end 134 of theshaft 124 is connected to a slide 136. The slide 136 is slidable withinan anti-rotate linear guide 138. The linear guide 138 is mounted on anend of the housing 116 opposite the end cap 120, and the slide 136extends outwardly from the housing through the linear guide. The slide136 includes an anti-rotate feature 140 such as a spline, a ball spline,a square linear bearing or similar that is cooperable with an innersurface 142 of the linear guide 138. The cooperation of the anti-rotatefeature 140 and the guide inner surface 142 allows the slide to move ina linear direction along its axis in and out of the housing 116 whilepreventing the slide from rotating about its axis.

A distal end 144 of the slide 136 includes a connector 146 such as aquick release connector or similar. The roller hemming head 114 isconnected to the slide 136 by the connector 146. For example, theconnector 146 may include a through hole 148 in the slide distal end144, and the roller hemming head 114 may be secured to the slide 136 bya fastener 150 extending through the roller hemming head 114 and thethrough hole in the slide 136, and a keeper 152 engaged with thefastener.

The roller hemming head 114 includes at least one hem roller, and mayinclude a plurality of different hem rollers 154, 156 for performingdifferent roller hemming operations. For example, one of the rollers 154may be utilized for push-type roller hemming operations while the otherroller 156 may be utilized for pull-type roller hemming operations.Also, one of the rollers 154 may be configured to fit into locationswith small clearances, while the other roller 156 may be configured tohem locations having larger clearances. Further, the rollers may beconfigured to perform different types of hems, such as flat hems andrope hems. The hem rollers 154, 156 are mounted on the roller hemminghead 114 via bearings to allow for smooth rotation of the rollers.Although, the roller hemming head 114 is shown having two hem rollers,the roller hemming head may have one roller or more than two rollers.

When current is applied to the electromagnetic coils 122, the coils aresubjected to a force (in either a left or right direction as viewed inFIG. 1) that is dependent upon the direction of current flow and theresultant electromagnetic field. The electromagnetic coils 122, beingfixed, do not move, and the electromagnetic field generated by the coilsacts upon the moveable yokes 128 in an opposite direction, causing themoveable yokes 128 and attached shaft 124 to travel axially. The axialmovement of the shaft 124 causes the slide 136 to move into or out ofthe housing 116. Movement of the shaft 124 to the right causes the slide136 to move outwardly relative to the housing 116, while movement of theshaft 124 to the left causes the slide 136 to move inward. In turn, themovement of the slide 136 acts upon the connected roller hemming head114. Outward movement of the slide 136 provides a push force when thehem roller 154 is engaged with a panel to be hemmed. Likewise, inwardmovement of the slide 136 provides a pull force when hem roller 156 isengaged with a panel. Further, the amount of push or pull force exertedby the hem rollers 154, 156 can be adjusted by varying the amount ofcurrent applied to the electromagnetic coils 122, which varies theamount of inward or outward force acting on the slide 136. As themagnitude of the current is increased or decreased, the hemming forcealso increases or decreases.

With reference to FIG. 2, in a second embodiment of the presentinvention a magnetically actuated roller head 210 includes a linearactuator 212 and a roller hemming head 214 mounted on the linearactuator. Reference numbers similar to those of the first embodimentindicate similar features, and unless otherwise noted below, the secondembodiment has features similar to the first embodiment.

The linear actuator 212 includes a pair of opposing actuator members 258fixedly mounted within the inner bore 218 of the housing 216. Eachactuator member 258 may be an electromagnet including a cylindricalbobbin 260 mounted in the inner bore 218. A magnetic material 262 isdisposed within the bobbin 260, and a coil 264 is wound on the bobbin260. The shaft 224 extends through openings 266 in the bobbins 260 andis freely moveable therethrough. A rare earth magnet 268 is disposedbetween the opposing actuator members 258 and is fixed to the shaft 224.The rare earth magnet 268 is a strong, permanent magnet made from alloysof rare earth elements (lanthanides). Examples of rare earth magnetsinclude but are not limited to neodymium magnets and samarium-cobaltmagnets. The rare earth magnet 268 is polarized and has its north andsouth poles disposed in an axial direction relative to the shaft 224.For example, in the embodiment of FIG. 2, the north pole of the rareearth magnet 268 points to the right towards the roller hemming head214, and the south pole points to the left towards the end cap 220 ofthe housing 216.

Based upon the polarity of the rare earth magnet 268, the magneticallyactuated roller hemming head 210 is arranged for push type rollerhemming operations in which the hem roller 254 pushes against a panel tobe hemmed. Due to the strength of the magnetic field of the rare earthmagnet 268, the linear actuator 212 applies approximately 330 pounds offorce in a linear direction at steady state with no external power/force(zero current) applied to the actuator members 258. The actuator members258 control and assist the actuation force of the rare earth magnet 268.More specifically, the linear force transmitted by the linear actuator212 is adjustable in an increasing or decreasing manner by varying acurrent applied to the coils 264. When a current of greater thanapproximately 1 Amp is applied to the coils 264, the force exertedincreases relative to the input value as follows: 1 Amp=360±10 pounds offorce, 2 Amps=390±10 pounds of force, and 4 Amps=440±10 pounds of force.When a current of less than −1 Amp is applied to the coils 264 (i.e.,less than 1 Amp in an opposite flow direction), the force exerteddecreases relative to the input value as follows: −2 Amps=280±10 poundsof force, and −4 Amps=230±10 pounds of force.

Alternatively, as shown in FIG. 3, the polarity of the rare earth magnet268 can be reversed, i.e. the rare earth magnet may be disposed suchthat the south pole of the rare earth magnet points to the right towardsthe roller hemming head 214, and the north pole points to the lefttowards the end cap 220 of the housing 216. In this arrangement, themagnetically actuated roller hemming head 210 is arranged for pull typeroller hemming operations in which the hem roller 256 is pulled toward apanel to be hemmed. At steady state, the amount of pull force isapproximately 330 pounds, and the pull force can be varied from thesteady state value by application of current to the coils 264.

With reference to FIG. 4, in a third embodiment of the present inventiona magnetically actuated roller head 310 includes a linear actuator 312and a roller hemming head 314 mounted on the linear actuator. Referencenumbers similar to those of the first embodiment indicate similarfeatures, and unless otherwise noted below, the third embodiment hasfeatures similar to the first embodiment.

The linear actuator 312 includes a pair of opposing actuator members370, 372 fixedly mounted within the inner bore 318 of the housing 316.Each actuator member 370, 372 may be a polarized rare earth magnetdisposed in a non-magnetic cylindrical shell 374 that is mounted in theinner bore 318. The shaft 324 extends through openings 376 in the shell374 and is freely moveable therethrough. A rare earth magnet 368 isdisposed between the opposing actuator members 370, 372 and is fixed tothe shaft 324. A gap exist between the rare earth magnet 368 and theinner bore 318 of the housing 316. The rare earth magnet 368 ispolarized and has its north and south poles disposed in an axialdirection relative to the shaft 324. For example, in the embodiment ofFIG. 4, the north pole of the rare earth magnet 368 points to the righttowards the roller hemming head 314, and the south pole points to theleft towards the end cap 320 of the housing 316. Also, the north pole ofthe actuator member 370 points to the left and the south pole points tothe right, and the north pole of the actuator member 372 points to theright and the south pole points to the left. Therefore, the polarity ofthe actuator member 370, rare earth magnet 368, and actuator member 372as viewed from left to right in FIG. 4 is north-south, south-north,south-north.

Based upon the polarity of the actuator members 370, 372 and rare earthmagnet 368, the magnetically actuated roller hemming head 310 isarranged for push type roller hemming operations in which the hem roller354 pushes against a panel to be hemmed. The interactions (attractionand repulsion) of the magnetic fields of the actuator members 370, 372and rare earth magnet 368 result in approximately 330 pounds of outwardforce being applied to the slide 336 and in turn the hem roller 354. Thedistance between the actuator members 370, 372 and the rare earth magnet368 provides compliance for the hem roller 354 (i.e., allows the hemroller 354 to travel small distances to the left and right as viewed inFIG. 4). Also, the opposing polarities of the rare earth magnet 368 andthe actuator member 372 aid in maintaining a constant hemming forcethrough a stroke of the hem roller 354.

Alternatively, as shown in FIG. 5, the polarity of the rare earth magnet368 can be reversed, i.e. the rare earth magnet may be disposed suchthat the south pole of the rare earth magnet points to the right towardsthe roller hemming head 314, and the north pole points to the lefttowards the end cap 320 of the housing 316. Therefore, the polarity ofthe actuator member 370, rare earth magnet 368, and actuator member 372as viewed from left to right in FIG. 5 is north-south, north-south,south-north. In this arrangement, the magnetically actuated rollerhemming head 310 is arranged for pull type roller hemming operations inwhich the hem roller 356 is pulled toward a panel to be hemmed. Theamount of pull force is approximately 330 pounds, and the opposingpolarities of the rare earth magnet 368 and the actuator member 370 aidin maintaining a constant hemming force through a stroke of the hemroller 356.

In the third embodiment, the housing 316 and shaft 324 may benon-magnetic so as to not interfere or interact with the magnetic fieldof the rare earth magnets.

Although the invention has been described by reference to specificembodiments, it should be understood that numerous changes may be madewithin the spirit and scope of the inventive concepts described.Accordingly, it is intended that the invention not be limited to thedescribed embodiments, but that it have the full scope defined by thelanguage of the following claims.

1. A magnetically actuated roller head comprising: a linear actuatormountable on an end of a multi-axis robotic arm; said linear actuatorincluding a slide, a magnet operably connected to said slide andoperable to urge said slide in a linear direction, and a connectordisposed on a distal end of said slide; and a roller hemming headmounted on said linear actuator by said connector, said roller hemminghead including at least one hem roller.
 2. The magnetically actuatedroller head of claim 1, wherein said magnet is a rare earth magnet. 3.The magnetically actuated roller head of claim 1, wherein said linearactuator includes a rare earth magnet disposed between two opposingmagnets, the polarity of one of said opposing magnets is disposed in thesame direction as the polarity of said rare earth magnet and thepolarity of the other of said opposing magnets is disposed in anopposite direction to the polarity of said rare earth magnet.
 4. Themagnetically actuated roller head of claim 3, wherein said two opposingmagnets are rare earth magnets.
 5. The magnetically actuated roller headof claim 1, wherein said linear actuator includes an electromagnetdisposed on each of opposite sides of said magnet, said electromagnetscontrolling and assisting a force transmitted by said magnet.
 6. Themagnetically actuated roller head of claim 1, wherein said slideincludes an anti-rotate feature.
 7. A magnetically actuated roller headcomprising: a housing including an internal bore, said housing beingmountable on an end of a multi-axis robotic arm; a pair of opposingactuator members fixedly mounted within said inner bore; a shaftextending through said actuator members; a magnet mounted on said shaftand moveable within said inner bore, said magnet being disposed betweensaid actuator members; a slide connected to said shaft and extendingoutwardly from said housing; a connector disposed on a distal end ofsaid slide; and a roller hemming head mounted on said connector, saidroller hemming head including at least one hem roller; whereby saidactuator members control and assist a hemming force applied by saidroller hemming head through said magnet.
 8. The magnetically actuatedroller head of claim 7, wherein said magnet is a rare earth magnet. 9.The magnetically actuated roller head of claim 7, wherein said actuatormembers are rare earth magnets.
 10. The magnetically actuated rollerhead of claim 9, wherein the polarity of one of said actuator members isdisposed in the same direction as the polarity of said rare earth magnetand the polarity of the other of said actuator members is disposed in anopposite direction to the polarity of said rare earth magnet.
 11. Themagnetically actuated roller head of claim 7, wherein said actuatormembers are electromagnets.
 12. The magnetically actuated roller head ofclaim 7, wherein said housing includes an anti-rotate linear guide, andsaid slide includes an anti-rotate feature cooperable with said linearguide.
 13. The magnetically actuated roller head of claim 12, whereinsaid anti-rotate feature is one of a spline, a ball spline, and a squarelinear bearing.
 14. A method of roller hemming comprising the steps of:mounting a linear actuator on an end of a multi-axis robotic arm, saidlinear actuator including a slide, a magnet operably connected to saidslide and operable to urge said slide in a linear direction, and aconnector disposed on a distal end of said slide; and mounting a rollerhemming head on said linear actuator by said connector, said rollerhemming head including at least one hem roller; whereby said linearactuator provides a hemming force for performing roller hemmingoperations with said hem roller.
 15. The method of claim 14, whereinsaid magnet is a rare earth magnet.
 16. The method of claim 14,including the step of: disposing said magnet between a pair of opposingactuator members.
 17. The method of claim 16, wherein said actuatormembers are rare earth magnets.
 18. The method of claim 16, wherein saidactuator members are electromagnets.
 19. The method of claim 14,including the step of: restricting axial rotation of said roller hemminghead by providing a spline on said slide.
 20. The method of claim 14,including the step of: providing a plurality of different hem rollers onsaid roller hemming head.